Dwarfism in plants can be achieved by artificial mutagenesis via chemicals and radiation. However, these methods cause undesirable mutations in genes other than the gene involved in plant dwarfism. Moreover, the dwarf phenotype is largely hetero-recessive and therefore it is difficult to select desired transformed plants when additional genetic traits are to be added.
The dwarfism techniques employing recent biotechnology procedures can overcome the problems described above, in which plant shapes are controlled by introducing a single specific gene or antisense DNA into plants. The dwarf phenotype is inherited by subsequent generations as a dominant trait according to Mendelian inheritance.
A known method for controlling plant shapes using biotechnology is that of controlling gibberellin biosynthesis. For example, a method of dwarfing a plant by introducing the gibberellin 2β hydroxylase gene into the plant has been reported (Sakamoto T, et al., Plant Physiol., 25: 1508–1516, 2001). A method for semi-dwarfing a plant by introducing the antisense DNA against the gibberellin 3β hydroxylase gene into the plant has also been reported (Ito H, et al., Proc. Natl. Acad. Sci. USA, 98: 8909–8916, 2001).
Brassinosteroids are a new class of plant hormones which function to enhance plant cell division, elongation and differentiation. Research of brassinosteroids has been underway, but the molecular mechanism of action thereof is not yet fully understood.